DESCRIPTION: The continuing studies employing different means to induce glucose regulated stress protein GRP78, such as treating cells with 2-deoxyglucose or 6-aminonicotinamide, clearly demonstrate that induction of GRP78 in V79 Chinese hamster cells is associated with potentiation of cytotoxicity inflicted by BCNU, cisplatin or melphalan as determined by clonogenic survival assays. Enhanced sensitivity to these platinating/alkylating agents, observed following GRP78 induction, is associated with an impairment of DNA cross-link repair. Further, this increase in sensitivity associated with up-regulation of GRP78 is also observed in three different human colon cancer cell lines, each bearing genetic defects, such as mutated p53, defective mismatch repair, or deficiency in O6-alkylguanine-DNA-alkyltransferase (AGT). Thus, it appears that the approach of overexpression/upregulation of GRP78, a strong Ca2+-binding protein may be useful in potentiation of cytotoxicity induced by alkylating/platinating agents. The proposal involves an investigation to determine the mechanisms of association of GRP78 induction with alkylating/platinating in various human cancer cell lines by examining the following specific questions: 1) Is the association true for human cancer cell lines originated from various tissues?; 2) What are the consequences of GRP78 induction on alkylating agent-induced apoptosis?; 3) Does GRP78-dependent increased sensitivity stem from impairment in removal of DNA adducts or DNA cross-link repair?; 4) Does GRP78 directly participate in DNA repair? and; 5) Is induced GRP78 itself the cause of increased sensitivity or is it the result of activation, or do pathways that lead to GRP78 induction and augmented sensitivity (e.g., alteration in Ca2+ homeostasis) overlap? The study is expected to provide an increased understanding of the mechanisms of GRP78 modulation of molecular and cellular responses to cancer chemotherapeutic agents that will allow strategies for transferring benchside results to the bedside.